All 10 questions from the Post-UTME Screening (Post-UTME) Physics 2011 Objective paper, with the correct answer and a full explanation for each. Free, no signup needed.
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A household refrigerator is rated 200 watts. If electricity costs 5k per kWh, what is the cost of operating it for 20 days?
Energy=200W×24hr×20days=96kWh. Cost=96×5kobo=480kobo=N4.80.
The principle of operation of an induction coil is based on
Induction coils work via electromagnetic induction, governed by Faraday's law.
A block and tackle system is used to lift a load of 20N through a vertical height of 10m. If the efficiency of the system is 40%, how much work is done against friction?
Efficiency=output/input×100: 40=(20×10)/input×100, so input=500J. Work against friction=input-output=500-200=300J.
The pressure on the gas of a constant gas thermometer at the ice point is 325mm of mercury and at the steam point 875mm of mercury. Find the temperature when the pressure of the gas is 190mm mercury.
Using the linear gas-pressure temperature relation between the ice and steam points, the corresponding temperature works out to 243K (-30°C).
Which of the following is a fundamental (base) unit?
The second is one of the SI base units; Newton, Watt, and Joule are all derived units.
A car moving with a speed of 90km/hr was brought uniformly to rest by the application of the brakes in 10s. How far did the car travel after the brakes were applied?
Initial speed=25m/s, decelerating uniformly to rest in 10s gives a=-2.5m/s². Distance=ut+½at²=25(10)-½(2.5)(100)=250-125=125m.
A body of mass 100g moving at a velocity of 10.0ms⁻¹ collides with a wall. If after the collision it moves with a velocity of 2.0ms⁻¹ in the opposite direction, calculate the change in momentum.
Initial momentum=0.1×10=1Ns; final momentum=0.1×(-2)=-0.2Ns. Change=|-0.2-1|=1.2Ns.
A trough 12.0cm deep is filled with water of refractive index 4/3. By how much would a coin at the bottom of the trough appear to be displaced when viewed vertically from above the water surface?
Apparent depth=real depth/n=12/(4/3)=9cm. Displacement=12-9=3cm.
A wire of length 15m made of a material of resistivity 1.8×10⁻⁶Ω·m has a resistance of 0.27Ω. Determine the area of the wire
A=ρL/R = (1.8×10⁻⁶×15)/0.27 = 1.0×10⁻⁴m².
After three half-lives, the fraction of a radioactive material that has decayed is
Remaining fraction=(½)³=1/8, so decayed fraction=1-1/8=7/8.
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